This invention pertains to a method and apparatus for attaching a flexible circuit to the surface of an ink-jet pen.
Certain ink-jet printers, such as that manufactured by Hewlett-Packard Company and designated the "DeskJet," use replaceable pens. The pens are of the thermal ink-jet type and comprise an ink reservoir that is in fluid communication with a print head that is mounted to the pen body. An orifice plate defines the exterior surface of the print head. The plate includes a plurality of orifices that are shaped as nozzles through which ink drops are discharged. Each nozzle has associated with it a resistor that is selectively driven (heated) with sufficient current for vaporizing ink in the vicinity of the nozzle, thereby forcing through the nozzle a drop of ink.
Electrically conductive lines or "traces" are carried on a thin, flexible plastic strip that is mounted to the exterior of the pen. The composite of the flexible strip and traces is hereafter referred to as a flexible circuit. The traces each connect at one end with a lead on the print head that carries current to a nozzle resistor. The other end of each trace terminates in a contact pad.
The contact pads on the pen-mounted flexible circuit connect with contacts on a corresponding circuit that is mounted to a carriage that holds the pen within the printer. Signals for driving the nozzle resistors are generated by a microprocessor and associated drivers that apply the signals to the resistors via the flexible circuit traces.
In the past, the flexible circuit was attached to the pen body by a thermoplastic adhesive that was applied in the form of discrete patches between the flexible circuit and the pen body. One problem with the use of the adhesive technique is that it is difficult to apply the adhesive uniformly across the entire surface area of the flexible circuit. Areas of the flexible circuit that receive no adhesive, particularly the edges and corners of the circuit, may lift from the pen surface, thereby causing the circuit to peel from the pen body when the pen is manipulated by the user or moved by the printer carriage. Moreover, the adhesive may re-melt in the event the pen is exposed to a high-temperature environment.
In the process of manufacturing a black-ink pen for a DeskJet ink-jet printer, the ink reservoir is filled and the print head is primed. Specifically, suction is applied to the exterior of the orifice plate after the pen reservoir is filled with ink. The suction draw ink from the reservoir through the nozzles to remove air so that the print head will operate properly. One mechanism for applying the suction to the nozzles includes a flexible cap that is pressed against the orifice plate to substantially enclose the nozzles so that they are in fluid communication with a small internal chamber defined by the cap. Suction is then applied to the chamber. Once the pen is primed, the suction and cap are removed.